Urokinase mediates endothelial cell survival via induction of the X-linked inhibitor of apoptosis protein.
Urokinase-type plasminogen activator (uPA) additionally elicits a whole array of pro-angiogenic responses, such as differentiation, proliferation, and migration. In this study, we demonstrate that in endothelial cells uPA also protects against apoptosis by transcriptional up-regulation and partially by mRNA stabilization of inhibitor of apoptosis proteins, most prominently the X-linked inhibitor of apoptosis protein (XIAP). The antiapoptotic activity of uPA was dependent on its protease activity, the presence of uPA receptor (uPAR) and low-density lipoprotein receptor-related protein (LRP), but independent of the phosphatidylinositol 3 (PI3) kinase pathway, whereas vascular endothelial growth factor (VEGF)-induced antiapoptosis was PI3 kinase dependent. uPA-induced cell survival involved phosphorylation of p21-activated kinase 1 (Pak1) and the IkappaB kinase alpha that leads to nuclear factor kappaB (NF-kappaB) p52 activation. Indeed, blocking NF-kappaB activation by using specific NF-kappaB inhibitors abolished uPA-induced cell survival as it blocked uPA-induced XIAP up-regulation. Furthermore, down-regulating XIAP expression by small interfering RNA (siRNA) significantly reduced uPA-dependent endothelial cell survival. This mechanism is also important for VEGF-induced antiapoptosis because VEGF-dependent up-regulation of XIAP was found defective in uPA(-/-) endothelial cells. This led us to conclude that uPA is part of a novel NF-kappaB-dependent cell survival pathway.
Prager
Gerald W
GW
Department of Vascular Biology and Thrombosis Research, Centre for Bio-Molecular Medicine and Pharmacology, Medical University Vienna, Vienna, Austria.
Mihaly
Judit
J
Brunner
Patrick M
PM
Koshelnick
Yuri
Y
Hoyer-Hansen
Gunilla
G
Binder
Bernd R
BR
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002470:Cell Survival; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism; D015151:Immunoblotting; D007124:Immunoenzyme Techniques; D047468:Immunoprecipitation; D026503:Low Density Lipoprotein Receptor-Related Protein-1 / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D016328:NF-kappa B / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D020871:RNA Stability; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D055293:Receptors, Urokinase Plasminogen Activator / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D014568:Urokinase-Type Plasminogen Activator / Q000502:physiology*; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D054462:p21-Activated Kinases / Q000378:metabolism
D026503:Low Density Lipoprotein Receptor-Related Protein-1; D016328:NF-kappa B; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D055293:Receptors, Urokinase Plasminogen Activator; D042461:Vascular Endothelial Growth Factor A; D051636:X-Linked Inhibitor of Apoptosis Protein; D019869:Phosphatidylinositol 3-Kinases; D054462:p21-Activated Kinases; D051550:I-kappa B Kinase; D014568:Urokinase-Type Plasminogen Activator